This invention relates to an improvement of solid-state image sensors, and particularly to a solid-state image sensor in which the blooming phenomenon is suppressed.
Attention has been paid to the solid-state image sensor for home VTR camera or industrial camera. Particularly, a solid-state image sensor with a photoconductive film, in which a photoconductive film is used as a light-sensitive section and signal processing is made by a Si scanning device, has a high sensitivity and no smearing and therefore it is said to be most suitable particularly to small-sized cameras.
The Si scanning device now used is mainly of the MOS type in which MOS switching elements are arranged in a matrix array and signals are read from a diode section formed of PN junctions by a shift register, and of the charge transfer type in which signals from a diode section formed of PN junctions are read in a charge transfer device (charge coupled device (CCD) or bucket brigade device (BBD)) by MOS FET and then transferred to an output state.
Particularly when a scanning device of charge transfer type is combined with a photoconductive film, the charge carrying capacity is usually smaller than the amount of signal charge produced in the photoconductive film, and thus much care must be taken to the processing of the signal charge. However, studies as to the above processing are actually insufficient so that the blooming phenomenon is not suppressed yet in this type of solid-state image sensor.